Bone Growth Notes

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Bone Growth Notes
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Ossification

• Process of bone formation
• 2 types
• Intramembranous
• Occurs directly in connective tissue membranes
• Flat bones of skull, mandible clavicles
• Fontanels soft spots still membrane

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• Endochondral
• In embryos, skeleton is primarily hyaline
  cartilage
• During development, much of this cartilage is
  replaced by bone
• Most bones form this way

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Bone Growth

• Epiphyseal plates allow for growth of long bone
  during childhood
• New cartilage is continuously formed
• Older cartilage becomes ossified
• Cartilage is broken down
• Bone replaces cartilage

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• Appositional growth growth in thickness new
  bone added by periosteal osteoblasts

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Types of Bone Cells

• Osteocytes
• Mature bone cells
• Osteoblasts
• Bone-forming cells
• Osteoclasts
• Bone-destroying cells

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Remodeling

• Bone is continually being broken down changed
  (reformed)
• Balance between actions of osteoclasts and
  osteoblasts

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Hormonal Control

• Growth hormone produced by pituitary gland
• Thyroid hormone stimulates epiphyseal plate
  closure
• Not enough, affects growth
• Plate closer stops growth

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• Testosterone and estrogen
• Plate closure
• Osteoporosis in old age
• Calcitonin secreted by thyroid inhibits
  osteoclasts and stimulates osteoblasts decrease
  blood Calcium

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• Parathyroid hormone stimulates osteoclasts and
  increased blood calcium